One of the most severe of Roman Military punishments, "Decimatio" (which would evolve into the word "Decimate" or "Decimation"), was an execution method used for Cowardice, Mutiny and Desertion. The Latin root word "Deci" (or the numeral "10"), was applied to every 10th soldier from the violating Unit. Normally, Decimatio was applied to a Cohort (or roughly 480 men).
Documented as first being used around the 4th Century BC, it's execution method could be accomplished by two procedures. The first involved all other Soldiers NOT selected, who were forced to gather stones or rocks. These men were ordered to "stone to death" (or batter), the selected victims. Another method was the using of Brass Spikes. These would be placed at the base of the spine and brain, upon which - a single blow would dispatch the violator.
The bodies of the executed would be unceremoniously buried in an unmarked mass grave. No honors were granted. A list of the Decimated would be sent to Rome for Public display. The Act was performed to show other Soldiers the fate that awaited them, should they commit certain acts against Roman Military "Law", in the future.